Narco or "drug subs" started showing up in the Pacific and Caribbean in 2006.
Since that time, the use of these low tech submersibles has increased and is a popular method to smuggle drugs into the United States. I just read a great article from the United States Naval Institute about the work being done by the US Coast Guard on this front.
The article reports Coast Guard officials have stopped 33 of these "drug subs", carrying a combined 200 metric tons of cocaine.
Here is a link to the article (with video of a drug sub being stopped): http://news.usni.org/news-analysis/drug-subs-caribbean-littorals